Acoustic apparatus



June 24, 1930.

w. J. O'LEARY' Acouswic APPARATUS Fiiea D9924. 1927' INVENTOR.

A TTORNEYS.

Patented 'ilune 24, 1930 WILLIAM J. OLEARY, OF DAYTON, OHIO Acous'rrc ArrAaArus Application filed December 24, 1 927. Serial Ito-242,402.

This invention relat s to electrical acoustic apparatus and is particularly concerned with electrical sound reproducers.

One, object of the invention is the provision of an electrical sound reproducer which may be used for the productionpf sound from phonograph records, embodying a coil in a magnetic field moved by the vibrational movements of a stylus which is directly connected to it. 1

Another object of the inevntion is the provision of an electrical sound reproducer of the type mentioned, embodying a coil supportingshaft which is supported by rubber mounting means.

Other objects'and advantages of the invention will be apparent from the following description and from the drawings in whic t Fig. 1 is a side elevation of the operating parts of the present-invention; 1

Fig. 2 is a general View of a phonograph reproducer associated with a sound record;

Fig. 13 is a section on the line 33 of Fig. 1;

Fig. 4 is a section on the line 4-4 of Fig. ,1 showing the rubber mounting block;

Fig. 5 is a section on'the line 55'0f Fig. 1; and

Fig. 6 is an enlarged section through the 001 Referring more particularly to the drawings, the electrical sound reproducer comprises a case 10 in which the operating parts of the apparatus shown. in Fig. 1 are mounted. This case is'suitably supported upon a tone arm 11 which'is adapted to as shown in Fig. 6is not continuous around shaped magnet having adjacent poles 18 and 19. Between the poles is a fixed iron armature 20, so arranged as to provide two small air gaps 21 and22 between'it and the two poles of the magnet. The armature is fixed in position by means of a plate 23 of brass or other suitable non-magnetic material which is attached to the armature and to the magnet by means of suitable screws 24. The plate 23 is bent to provide a seat 26 in which is tightly fitted a rubber mounting block 27 located adjacent the armature 20. The opposite part .of;the magnet is provided with a rubber block 3Q,"tightly seated therein, and within the two blocks 27 and 30 are shaft receiving openings which snugly receive a shaft 31 and which are effective in yieldingly restraining movements of this shaft in any direction. The end of the shaft which rests in block 27 is preferabljprovided with a fiat side as indicated at 32 to prevent any substantial twisting m'ove-' merits of the shaft in relation to the rubber block and thus maintain the normal position of the shaft yieldingly. The'shaft extends between-the rubber mountingblocks, passing through a central bore 29 in the armature of somewhat larger size than the diameter of the shaft, and supported by the shaft adjacent the poles of the magnet is a coil of wire 35- preferably consisting of a number of turns passing around and supported by a brass shell 33 and spaced from the armature 20 as shown in the drawings. The shell 33 the entire coil but on the contrary. is pro- .vided with a gap 34 so that a complete metalrotate about the vertical axis .12 in the customary manner,'the mounting of the case 10 being such that it may move vertically and "may be swung laterally so as to follow the 1'novemetits of the record indicated at 13. This record may be of any desired type but as shown, it is of the kind in, which the grooves are transversely cut.

Within the case and fixed thereto by suitable screws 16 is a'magnet 17. This magnet may be :of any desired type effective in the production'of a magnetic field, and as shown in the drawings, is a permanent horse-shoelic circuit is not formed by the shell. The

upper and lower'ends of the shell through which the shaft 31 extends are fixed to the shaft inany suitable manner. The terminal ends of thecoil extend as shown at 36 so that they maybe conveniently attached to electrical devices in a suitable circuit for the reproduction of sound. The coil 35 has its axis corresponding with the longitudinal axis of theshaft 31 and the coil is so mounted in the magnetic field which is effective across the two air gaps 21 and 22,

that when it is rotationallyoscillated, electrio currents will be generated in the coil bly are all firmly attached a rigid manner and will flow through the terminal ends 36 *to one another there is absolutely no possito a suitable amplifying or reproducing apparatus such as an audion tube amplifier or a sound producing unitl The shaft 31", as previously mentioned, is mounted at one end as indicated at 38 in the rubber block 27, and it projects through the shaft and is provided with means such as a thumb screw 40 and a receiving opening so that a stylus 41 may be mounted therein in fixed position, with the axis of the stylus somewhat displaced from the axis of the shaft 31. The shaft 31, the coil 35, the stylus holder and the stylus are all of light Weight and collectively provide an assembly' or movable element having a small movement of inertia about the axis of the shaft 31.

Fixedto and depending from the magnet 17 is an arm 42 of such length as to engage and ride in the top'of the grooves of the record in which the sound cuts are provided. The lower end of arm 42 is comparatively large and rounded so it may slide along the top of the grooves without being affected by and without affecting the sound or reproducing cuts. This arm is therefore effective in guiding the tone arm thus keeping the center of' shaft 31 always located in the center of the groove, and also operates to relieve a part of the weight of the'apparatus from the stylus. In order to play hill and dale records the apparatus is mounted atan angle of 90 .from that shown in the drawings, and in that case thearm or guide 42 must then be placed in line with the'center of the stylus.

As is readily'seen the device is reversible in operation and variations of current in the electrical transforming means may be used to produce mechanical oscillations of the stylus'for cutting records from which sound may be reproduced. When used for the creation of electrical current oscillations the vibrational movements of the stylus 41 as the latter operates in the transversely cut grooves of the phonograph record 13 is ef-* fective in the production of oscillations of the movable assembly formed of the shaft and the parts fixed to it, and the coil is thus rotationally oscillated in the magnetic field so that currents are generated in'the coil stylus is about an axis which is normal to a line tangential tothe groove of the record. As the various parts of the movable assemseveral parts are pivotally connected to one Where the actual movements are excessively slight as compared with the clearance found in a pivotal connection, the sound WlllCll 1s another, and in. a devic of this character produced in the device connected 'to the terminals .36 of the coil will be accurate reproductions of the sound waves corre-. sponding to the grooves in the record. The shaft 31 is efficiently supported by the rubber blocks 30 and 27 so that the movable assembly of the r'eproducer will have no movable assembly will not tend to continue to oscillate at any particular frequency by reason of its own torsional period of vibra fixed, period of oscillation. That is, the

- tion. The rubber forms a support acting to return the movable assembly to its normal position and 'yieldingly tend to hold it. there against the efforts of the stylus. The manner in which the movable assembly is constructed and mounted in place provides for ease in construction and cheapness in manufacture and avoids delicate pivotal'mountings and delicate springs, and avoids torsional vibrational periods of oscillation al- Ways present when such springs are employed.

Whilethe form of'apparatus herein. described constitutes a preferred embodiment @of the invention, it is to be understood that the invention is not limited to this precise' form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An electrical sound reproducer for phonographs comprising a magnet, a-coil' rotatably mounted in the field of'the magnet, a shaft on which said coil is fixed with with the axis of the shaft, a rubber block mounted in said magnet, and snuglyreceiving said shaft to mount the shaft for rotational oscillations, a rubber mounting block supporting one end of the shaft adjacent the axis of rotation of the coil coinciding said coil, and a stylus-holder fixed to the other-end of said shaft and adapted to receive a stylus with its axis displaced from the axis of the shaft, whereby oscillations. of the stylus are transmitted through said shaft to the coil to cause the generation of currents in the coil.

2. An electrical sound reproducer for phonographs comprising a permanent mag net, a coil rotatably mounted in the field of the inagnet, a fixed iron armature within said coil, a shaft on which said coil is fixed with the axis of rotation ofthe coil coinciding with the axis of the shaft, 1 a rubber i v mounting block mounted in said magnet,

and snugly receiving said shaft to mount the shaft for rotational oscillations, a rubber mounting block supporting one end of the shaft adjacent said coil, said blocks providing the sole means for urging the shaft and the coil to a normal positlon, and a stylus holder fixed to the other end of said shaft and adapted to receive a stylus with its axis displaced from the axis of the shaft, whereby oscillations of the stylus are transmitted through said shaft to the coil to cause the generation of currents in the coil.

3. In a device of the class described, the combination of a permanent magnet with opposed pole pieces, a stationary'armature mounted between said pole pieces to provide a pair of air gaps, saidair gaps comprising sections of a tubular space formed by concave faces on the poles of the magnet and convex faces on the armature, a shaft extending through said armature with the axis of the said shaft coincidingwith the axis of said tubular space, a coil of insulated wire mounted upon said shaft and-with the sides of said coil extending through said air gaps, resilient means for supporting said shaft to permit slight tortional movements T thereof, and a stylus carried by said shaft whereby said shaft is oscillated when said stylus cooperates with a groove of a moving phonograph record.-

4. In a device of'the class described, the combination of a permanent magnet with opposed pole pieces, a stationary armature carried by said magnet and mounted between said pole pieces to provide a pair of air gaps, said air gaps comprising sections of a tubular s ace formed by concave faces on the poles o the magnet and convex faces on the armature, a shaft extending through said armature with the axis of the saidshaft coinciding with the axis .of said tubular space, a coil of insulated wire mounted upon said shaft and with the sides of said coil extending through said air gaps, resil-' .i'ent rubber bearings carried by sa1d magnet for supporting said shaft to permit slight tortional movements thereof, means tending to normally resist said torsional movements, and a stylus carried by said shaft whereby said shaft is oscillated when said stylus cogroove of a movingphono- 5. A device of the class described comprising in combination a permanent magnet in the form of a broken ring with the poles of said magnet opposed to each other,- a 'sta tionary armature mounted between said poles to provide a pair of narrow air ga s','

a shaft having the axis thereof substantia ly midwaybetween said air gaps, a coil carried by said shaft and extending through said air gaps, a resilient thrust bearin on the upper end ofsaid shaft, and aresi ient tortional bearing for the lower portion of said shaft, and a stylus carried by said shaft in such manner as to cause oscillatory movements to said shaft when said stylus is properly associated with. a groove of a moving phonograph record.

lower portion of'said shaft, and a stylus car- I ried bys'aid shaft in such manner as to cause oscillatory movements to' said shaft when said stylus is properl associated with a groove of a moving p onograph record.

-7. In .a device of the class described, in combination a magnet having opposed pole pieces, a shaft located in substantially the mid distance between said pole pieces, a coil of insulated wire carried by said shaft in a such manner that the lines of force fromv "said pole pieces out two sidesof said coil,

a resilient thrust bearing for the upper end of said shaft, and a resilient tortional bearing for the lower portion of said shaft, means to normally resist twisting of said shaft and to tend to hold said coil'in position between said pole pieces, and means for rotatably oscillating said shaft when said last mentioned means cooperates with the groove of a moving phonograph record.

8. In a device of the class described, in combination a magnet having opposed pole pieces, a shaft located in substantially the mid distance between said pole pieces, a coil of insulated wire carried by said shaft in such manner that the lines of force from said pole pieces cut two sides ofsaid coil, a resilient thrust bearing for the upper end of said shaft, said thrust bearing being carried by said magnet, and a resilient tortional bearing for the lower portion of said shaft, said thrust bearing being mounted in said magnet, means to normally resist twisting of said shaft and to tend to hold said coil in position between said pole pieces, and means for rotatably oscillating said shaftwhen said last mentioned means cooperates with the groove of a moving phonograph record.

9. An electrical pick-up unit for phonographs comprising in combination a permanent magnet of substantially circular form with opposed pole pieces, a shaft extending between sa1d pole ieces, a coil mounted upon said shaft, a t rust bearing for said shaft carried by said magnet, and

a tortional bearing for'said shaft carried by said magnet, whereby said magnet comprises a main frame for the operating parts of said unit. 7

10. An electrical pick-up unit for phonographs comprising in combination a ma at with opposed pole pieces, a shaft exten ing i between said pole. pieces, a coil mounted upon said shaft and having opposite sides between said pole pieces, a thrust bearing for said shaft carried by said magnet, and

a tortional bearing for said shaft carried by said magnet, whereby said magnet c0'm-- prises a main frame for the operating parts of said unit.

In testimony whereof I hereto afiix signature.

WILLIAM. J. oLEABi. 

